Irene made buns for sale. 55% of the buns were beef buns and the rest were chicken and mushroom buns in the ratio 3 : 1. If a customer bought 65% of the beef buns and all of the mushroom buns, what percentage of the chicken buns must Irene sell for her to maintain the original percentage of beef buns at first? Leave your answer in decimals and correct to 1 decimal place.

Beef buns	Chicken buns	Mushroom buns
11 u	9 u
	6.75 u	2.25 u

	Beef buns	Chicken buns	Mushroom buns	Total buns
Before	11 u	6.75 u	2.25 u	20 u
Change	- 7.15 u	- 3.6 u	- 2.25 u
After	3.85 u	3.15 u	0	7 u

55% = ⁵⁵₁₀₀ = ¹¹₂₀
65% = ⁶⁵₁₀₀ = ¹³₂₀

Total number of buns = 20 u

Number of chicken and mushroom buns
= 20 u - 11 u
= 9 u

Number of chicken buns at first
= ³₄ x 9 u
= 6.75 u

Number of mushroom buns at first
= 9 u - 6.75 u
= 2.25 u

Number of beef buns sold
= 65% x 11 u
= ⁶⁵₁₀₀ x 11 u
= ¹³₂₀ x 11 u
= 7.15 u

Number of mushroom buns sold
= ¹₄ x 9 u
= 2.25 u

Number of beef buns left 
= 11 u - 7.15 u
= 3.85 u

To maintain the percentage of the beef buns in the end, 
55% → 3.85 u
100% → ^3.85₅₅ x 100 = 7 u

Total number of buns in the end to maintain the original percentage of beef buns = 7 u

Number of chicken buns left
= 7 u - 3.85 u
= 3.15 u

Number of chicken buns that Irene must sell to maintain the original percentage of beef buns
= 6.75 u - 3.15 u
= 3.6 u

Percentage of the chicken buns that Irene must sell
= ^3.6_6.75 x 100%
= 53.3%

Answer(s): 53.3%